The objective of this research is the use of psychophysical and electrophysiological techniques to investigate the etiology of retinal and cortical disorders and to develop more sensitive tests for their diagnosis. Recent advances in psychophysical analysis and visual evoked potential techniques have greatly improved the sensitivity of these methods to detection of visual pathway dysfunction and determination of underlying mechanisms. Psychophysical techniques include flicker modulation sensitivity function, and two-dimensional spatial modulation sensitivity functions. Electrophysiological techniques involve measurement of the spatiotemporal modulation function for narrow-band visual evoked potential response. These methods have application to a wide range of visual disorders, from the retinal pathology to higher cortical dysfunctions. Clinical tests will be developed on the basis of experimental findings to assist in early diagnosis, differential diagnosis and therapeutic monitoring of visual disorders.